The present invention relates to an automatic shut-off device for a valve for compressed or liquefied gases comprising a valve body designed to be mounted on a gas cylinder and provided with an internal passage that allows the cylinder to be filled with pressurized gas.
Although not restricted thereto, the invention is more specifically aimed at a valve of the type described in Kerger, U.S. Pat. No. 5,282,496, the entire disclosure of which is hereby incorporated by reference in its entirety. This patent relates to a valve for refillable cylinders and which comprises a level-regulating valve to prevent it from being possible for the cylinder to be filled beyond a certain limit, for example 80% of its maximum capacity, so as to avoid potential risks of an accident.
However, there are still risks of an accident either if the cylinders are refilled by non-specialists and do not have level-regulating valves as proposed in the aforementioned patent, or if they are refilled with an inappropriate gas or if the user manages to neutralize the level-regulating valve, or even for other reasons.
The object of the present invention is to provide a simple and effective automatic shut-off device for a valve like the one described in the preamble and which prevents a gas cylinder from being filled by a non-specialist or unauthorized individual who does not possess special equipment.
In order to achieve this object, the invention provides an automatic shut-off device as described in the preamble which is characterized in that the internal passage has a widened cross section containing a ball sensitive to a magnetic field and of a diameter greater than the diameter of the passage and which acts as a non-return valve element by blocking the passage in the direction of filling, and in that said valve element can be neutralized by shifting the ball sideways under the effect of a magnetic field generated by a magnet placed on the outside of the valve.
In consequence, any attempt at filling the cylinder is bound to fail given that the ball, under the effect of its own weight and the pressure of the filling gas, is pressed against its seat which is formed by the upper edge of the passage and closes the passage toward the inside of the cylinder. Only somebody who knows how to open the passage and is in possession of an appropriate magnet will be able to carry out filling once he has moved the ball off its seat using this magnet.
Any attempt at filling the cylinder with the cylinder lying on its side is also bound to fail. Admittedly, by lying the cylinder down the passage can be opened because the ball, under the effect of its own weight, moves off its seat, but the pressure of the filling gas returns the ball onto its seat and automatically closes the passage.
According to one preferred embodiment, there is a tube made of synthetic material inside the axial passage. The upper edge of this tube serves to form the seat for the ball.
It is also possible to envisage a niche in the region of the ball in the exterior wall of the valve body and which is intended to accommodate a magnet of complementary shape. It is therefore necessary not only to have a magnet available to open the device but, in addition, this magnet has to have a special shape adapted to suit that of the niche.
The valve may also comprise means for preventing the ball from obstructing the upper passage above the widened cross section. These means may consist of a polygonal cross section of this passage or of a spring provided between this passage and the ball.